1. Technical Field
The present disclosure relates generally to bimetallic PGM catalyst systems, and, more particularly, to synergized PGM catalyst systems with lean and rich performance improvement.
2. Background Information
Carbon dioxide emitted from an internal combustion engine of an automobile and others has been a problem from the standpoint of protection of the global environment. A lean burn engine using less fuel provides a promising solution to this problem.
TWC systems may include bimetallic catalysts, which may be based on Platinum group metals (PGMs), including Pt—Rh, Pt—Pd, Pd—Rh, among others. A catalyst including a NOx storage material, such as alkali metals, as well as noble metals, which are normally used as a catalyst for purifying NOx and CO included in exhaust gas. This type of catalyst may absorb NOx included in the exhaust gas into the NOx storage material. When fuel concentration in the exhaust gas becomes rich, the absorbed NOx is removed by the action of the noble metal.
Since the fuel concentration in the exhaust gas of the aforementioned lean burn engine is low, conventional catalyst has been unable to sufficiently purify NOx. Also, due to a low melting point of alkali metal as the NOx storage material, the alkali metal migrates and is solid-solutioned into the catalyst substrate when the catalyst is heated to high temperatures. As a result, performance of the catalyst is lowered.
Therefore, there is a need to provide improved synergized PGM catalyst systems for exhaust gas purifying catalyst that may include bimetallic PGM catalyst to exhibit high NOx and CO purification performance even in a lean burn engine, and that do not allow deterioration of catalytic performance at high temperatures, improving the nitrogen oxide conversion under stoichiometric operating conditions and especially under lean operating conditions which may allow reduced consumption of fuel.